Most networks have a finite quantity of network resources available to support communication between endpoints. When these network resources are scarce, i.e., currently allocated to support existing calls or sessions, the establishment of new calls or sessions over these networks typically requires that some of the currently allocated network resources become available.
Networks in certain industries, such as the military and emergency services, actively manage their network resources according to a user-based priority scheme, such as multilevel precedence and preemption (MLPP). These networks associate a precedence-level to each network user and re-allocate network resources or preempt existing calls in favor of new calls according to these user-based precedence-levels. For instance, when a higher precedence-level user places a call over a network that does not have adequate resources to support the call, the network will preempt one or more existing calls associated with lower precedence-level users. Although multilevel precedence and preemption helps to ensure that certain users will have priority to network resources, the preemption of existing calls typically results in an abrupt disconnection that often degrades the experience of lower precedence-level users.